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ABSTRACT: Ultrawideband (UWB) pulse radar with high range resolution is suitable for near-field sensing. Applications of UWB pulse radar include human body identification in blurry vision for security or rescue purposes and accurate spatial measurements for industrial products such as a reflector antenna. The synthetic aperture radar is still promising for these applications because it creates an accurate image even for near-field targets in free space. However, for complex-shaped or multiple objects, this algorithm suffers from increased shadow region because it employs only a single-scattered signal for imaging. To resolve this difficulty, this paper proposes a novel imaging algorithm based on aperture synthesis for double-scattered signals. In general, double-scattered waves include independent information on target points, which are not obtained by a single-scattered wave. Based on this principle, the proposed method effectively synthesizes the double-scattered signals and enhances the reconstructible range of a target shape, part of which becomes a shadow in the former approach. In order to enhance accuracy, a false image suppression approach based on the Fresnel zone theory is also incorporated in the proposed method. The results from numerical simulations and an experiment verify that our method significantly enhances the visible range of target surfaces without either a priori knowledge of target shapes or preliminary observation of their surroundings.
IEEE Transactions on Geoscience and Remote Sensing 01/2012; · 2.89 Impact Factor
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ABSTRACT: We demonstrate optical orthogonal time-frequency domain multiplexing (OTFDM), which inherits the advantages of high-speed OTDM and high-spectral-efficient OFDM. Single-Pol., 2-b/s/Hz, 160-Gb/s OTFDM-QPSK is achieved by optical time-domain processing.
Optical Communication (ECOC), 2011 37th European Conference and Exhibition on; 10/2011
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ABSTRACT: The dates of crop developmental stages are important variables for many applications including assessment of the impact of abnormal weather on crop yield. Time-series 250-m vegetation-index (VI) data acquired from the Moderate Resolution Imaging Spectroradiometer (MODIS) provide valuable information for monitoring the spatiotemporal changes of corn growth across large geographic areas. The goal of this study is to evaluate the performance of a new crop phenology detection method, namely, two-step filtering (TSF), for revealing the spatiotemporal pattern of specific corn developmental stages (early vegetative: V2.5; silking: R1; dent: R5; mature: R6) over an eight-year period (2001-2008) across Iowa, Illinois, and Indiana using MODIS derived Wide Dynamic Range VI data. Weekly crop progress reports produced by the U.S. Department of Agriculture National Agricultural Statistics Service (NASS) were used to assess the accuracy of TSF-based estimates of corn developmental stages. The results showed that the corn developmental stages could be estimated with high accuracy (the root mean squared error ranged from 4.1 to 5.5 days, the determination coefficient ranged from 0.66 to 0.84, and the coefficient of variation ranged from 2.1% to 3.7%) based on NASS-derived statistics on an agricultural statistics district level. In particular, the annual changes in the spatiotemporal patterns of the estimated silking stage had a high level of agreement with those of the NASS-derived statistics. These results suggested that the TSF method could provide local-scale information of corn phenological stages, which had an advantage over the NASS-derived statistics particularly in terms of the spatial resolution.
IEEE Transactions on Geoscience and Remote Sensing 07/2011; · 2.89 Impact Factor
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ABSTRACT: Near field radar employing ultrawideband (UWB) signals with its high range resolution has great promise for various sensing applications. It enables non-contact measurement of precision devices with specular surfaces like an aircraft fuselage and wing, or a robotic sensor that can identify a human body in invisible situations. As one of the most promising radar algorithms, the range points migration (RPM) was proposed. This achieves fast and accurate surface extraction, even for complex-shaped objects, by eliminating the difficulty of connecting range points. However, in the case of a more complex shape whose variation scale is less than a pulsewidth, it still suffers from image distortion caused by multiple interference signals with different waveforms. As a substantial solution, this paper proposes a novel range extraction algorithm by extending the Capon method, known as frequency domain interferometry (FDI). This algorithm combines reference signal optimization with the original Capon method to enhance the accuracy and resolution for an observed range into which a deformed waveform model is introduced. The results obtained from numerical simulations and an experiment with bi-static extension of the RPM prove that super-resolution UWB radar imaging is accomplished by the combination between the RPM and the extended Capon methods, even for an extremely complex-surface target including edges.
IEEE Transactions on Antennas and Propagation 06/2011; · 2.15 Impact Factor
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ABSTRACT: We realized a wide-passband multi-channel tunable optical dispersion compensator for 88 WDM signals with 50-GHz spacing by combination of an arrayed-waveguide and bulk gratings. It utilizes a novel optics arrangement for high wavelength resolution.
Optical Fiber Communication Conference and Exposition (OFC/NFOEC), 2011 and the National Fiber Optic Engineers Conference; 04/2011
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ABSTRACT: The signal transmission characteristics of the first practical hierarchical optical cross-connect with a terabit-scale throughput are clarified experimentally employing 10-Gb/s wavelength-division-multiplexed signals. The observed power penalty was less than 0.9 dB after a 4-hop signal transmission.
IEEE Photonics Technology Letters 12/2010; · 2.19 Impact Factor
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ABSTRACT: We propose a novel optical configuration for a multichannel tunable optical dispersion compensator (TODC) with channel-by-channel operation across the entire L -band. The TODC consists of a cyclic frequency arrayed-waveguide grating whose free spectral range coincides with the channel spacing, a bulk grating, and a liquid crystal on silicon. We achieved channel-by-channel compensation over 50 channels with a maximum chromatic dispersion of ±800 ps/nm.
IEEE Photonics Technology Letters 12/2010; · 2.19 Impact Factor
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ABSTRACT: This paper presents an electrooptic vector digital-to-analog converter (EO-DAC) for coherent synthesis of optical multilevel signals, such as quadrature-amplitude modulation (QAM) signals. For generation of an optical multilevel/QAM signal, the inphase (I) and quadrature (Q) components of a carrier lightwave should be orthogonally modulated in multi-levels. Conventionally, inphase-quadrature (IQ) orthogonal modulators have been utilized for this purpose. In the scheme, however, the symbol rate available for multilevel/QAM signals is limited, and it is difficult to obtain a clear constellation because of the difficulty involved in handling with electrical multilevel signals. The EO-DAC employing multiparallel modulator, described in this paper, can be used to synthesize multilevel signals through the combination of binary data streams. Using this proposed technology, multilevel signals can be coherently synthesized at a high bit rate, and clearer constellations can be obtained. Further, because of its flexibility, and versatility, the EO-DAC can be used for the several types of multilevel modulation formats. In this paper, we describe the EO synthesis of optical multilevel signals especially focusing on the method based on the EO-DAC, along with comparisons with other conventional methods.
IEEE Journal of Selected Topics in Quantum Electronics 11/2010; · 3.78 Impact Factor
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ABSTRACT: We demonstrated 95-Gb/s NRZ-DPSK modulation by using high-speed modulator and full-ETDM technique. The BER performance under a back-to-back condition is achieved to be 7.1 × 10<sup>-4</sup> at 95 Gb/s.
Optical Communication (ECOC), 2010 36th European Conference and Exhibition on; 10/2010
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ABSTRACT: Ultra-wideband (UWB) pulse radar is an effective device as the basis for building a high-precision surveillance system. The fast SEABED (Shape Estimation Algorithm based on BST and Extraction of Directly scattered waves) imaging algorithm is capable of accurately estimating target shapes using UWB pulse radar. A new UWB radar imaging algorithm, based on an extension of the SEABED algorithm that uses the motion of a target, was proposed in our previous work. This is unlike the conventional SEABED system that assumes a scanning antenna. Using a simple system with three fixed antennas, this imaging method has been verified as being viable even for targets with arbitrary motion. This study examines the performance limits of the method under various conditions. The numerical simulation establishes that the proposed method can accurately estimate the target shape even under severe conditions. Moreover, we clarify that the proposed method estimates a target shape with high accuracy and in a shorter time compared with conventional methods.
ICECom, 2010 Conference Proceedings; 10/2010
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ABSTRACT: We demonstrated broadband comb generation using a Mach-Zehnder-modulator-based flat comb generator with a feedback loop. By constructing the feedback loop, the modulation depth was increased. A generated comb signal was broadened as compared with single-path configuration.
Optical Communication (ECOC), 2010 36th European Conference and Exhibition on; 10/2010
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ABSTRACT: We demonstrate real-time homodyne demodulation of a 40-Gb/s BPSK signal by using novel digital optical phase-locked loop with a Costas-loop structure. The optical carrier is locally recovered in the receiver side with a slow-speed digital signal processor employing bandwidth-enhanced samplers.
Optical Communication (ECOC), 2010 36th European Conference and Exhibition on; 10/2010
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ABSTRACT: Ultra Wide-Band (UWB) pulse radar provides promise for surveillance systems via its high-range resolution. To realize a low-cost and high-quality indoor security system, we propose a UWB radar imaging system using indoor multipath echoes for targets in shadow regions. A multipath wave can be used as an approximation of an imaginary echo from a mirror image antenna to the target, ignoring phase rotation and attenuation. Conventional studies have only dealt with locating point-like targets, not estimating their shape. We apply interferometry using these mirror image antennas to estimate target shapes. If this method alone is applied, many false image points are estimated because it is difficult to determine uniquely the corresponding mirror image antenna to each echo. We propose an effective false-image reduction algorithm to obtain a clear image. Numerical simulations show that most of the false image points are removed and the target shape is accurately estimated.
Indoor Positioning and Indoor Navigation (IPIN), 2010 International Conference on; 10/2010
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ABSTRACT: Baroreflex regulates arterial pressure by modulating ventricular and vascular properties. We investigated if the framework of circulatory equilibrium that we developed previously (Am J Physiol 2004, 2005) by extending the classic Guyton's framework is capable of predicting baroreflex induced changes in arterial pressure. In animal experiments, we estimated open loop transfer functions of baroreflexly modulated ventricular and vascular properties, synthesized baroreflex induced dynamic changes in arterial pressure using the estimated transfer functions and compared the predicted responses with measured responses. We demonstrated that the predicted baroreflex induced changes in arterial pressure matched reasonable well with those measured. We conclude that the framework of circulatory equilibrium is generalizable under the condition where baroreflex dynamically changes arterial pressure.
Engineering in Medicine and Biology Society (EMBC), 2010 Annual International Conference of the IEEE; 10/2010
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ABSTRACT: For high range resolution acoustic vascular imaging we apply frequency domain interferometry and Capon method to a few frames of in-phase and quadrature (IQ) data acquired by a commercial ultrasonographic device. To suit the adaptive beamforming algorithm to medical acoustic imaging we employ three techniques; frequency averaging, whitening, and pseudo-double RF data conversion. The proposed method detected two couples of boundaries 0.26 and 0.19 mm apart using a single frame and two frames of IQ data, respectively, where each couple of boundaries is indistinguishable from a single boundary utilizing B-mode images. Further this algorithm could depict a swine femoral artery with higher range resolution than conventional B-mode imaging. These results indicate the potential of the proposed method for the range resolution improvement in ultrasonography, originating the progress in detection of vessel stenosis.
Engineering in Medicine and Biology Society (EMBC), 2010 Annual International Conference of the IEEE; 10/2010
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ABSTRACT: This paper describes sleep and adaptive link rate (ALR) control functions to reduce the power consumption of optical network units (ONUs) in 10 Gb/s Ethernet passive optical network (10G-EPON) systems. A hybrid mechanism that includes both sleep and ALR control functions is proposed with a view to further improving the power-saving performance. The sleep control function switches the ONU mode, i.e., active or sleep, depending on the presence or absence of traffic. The ALR control function switches the downlink rates between an optical line terminal (OLT) and an ONU, i.e., 1 Gb/s or 10 Gb/s, depending on the quantity of traffic. The proposed hybrid mechanism offers effective power management of ONUs on the basis of the traffic conditions. The proposed hybrid mechanism is validated by a numerical simulation and an experiment.
Journal of Optical Communications and Networking 10/2010; · 1.87 Impact Factor
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ABSTRACT: Near field radar employing UWB (Ultra Wideband) signals with its high range resolution is promising as various sensing applications. It enables robotic or security sensors that can identify a human body in invisible situations. As one of the most promising radar algorithms, the RPM (Range Points Migration) is proposed. This offers an accurate 3-D (3-dimensional) surface extraction for various target shape. However, in the case of a complicated target surface whose variation scale is less than wavelength, it still suffers from image distortion caused by multiple interference signals with different waveforms. As a substantial solution, this paper proposes a novel range extraction algorithm by extending the Capon, known as frequency domain interferometry (FDI). This algorithm combines reference signal optimization with the original Capon to enhance the accuracy and resolution for an observed range into which a deformed waveform model is introduced. The results obtained from numerical simulations and an experiment prove that super-resolution UWB radar imaging is achieved by the proposed method, even for an extremely complex-surface target, including edges.
Electromagnetic Theory (EMTS), 2010 URSI International Symposium on; 09/2010
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ABSTRACT: In this paper the authors describe the linear model validation strategy based on experimental tests of a new complex multi-roller web systems specially powered for running with high web speeds. The problem of validation has been dealt in using an optimization strategy for the estimation of several unknown model parameters. The experimental tests show the validity and accuracy of the procedure.
Mechanical and Electronics Engineering (ICMEE), 2010 2nd International Conference on; 09/2010
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ABSTRACT: A nonvolatile crossbar switch using a dual-layered TiO<sub>x</sub>/TaSiO<sub>y</sub> solid electrolyte, "NanoBridge," has been developed. NanoBridge is scalable to 50 nm and programmed at low voltage while keeping a low ON-resistance. The high compatibility with a back-end-of-line processing for CMOS integrated circuits is achieved by using the dual-layered TiO<sub>x</sub>/TaSiO<sub>y</sub> solid electrolyte, in which a barrier (Ti) is inserted on Cu and changes to an oxide during the subsequent process step. TiO<sub>x</sub> has the double role of preventing Cu oxidation during TaSiO<sub>y</sub> deposition and acting as a solid electrolyte itself. A resistive-change characteristic is investigated in terms of the inserted barrier dependence. At an optimal barrier insertion, the integrated switch shows bipolar switching characteristics with a high OFF-/ON-resistance ratio of 10<sup>6</sup>. The developed device is applied to a 4 × 4 crossbar switch integrated with the CMOS circuit. The crossbar switch is configured without select transistors and transfers signals properly.
IEEE Transactions on Electron Devices 09/2010; · 2.32 Impact Factor
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ABSTRACT: UWB (Ultra Wide-Band) radar systems are promising imaging tools covering a variety of application fields including surveillance systems. UWB radar technology can provide advanced capabilities for current surveillance systems. An imaging algorithm for UWB radars, the TR (Time-Reversal) method enables high-resolution imaging in a multipath environment. Conventional TR methods have been applied to antenna array systems while our previous work proposed a TR method with a low-cost single antenna-based system. In this study, we propose a radar system with a single antenna on a vehicle in a multipath environment. This vehicle is assumed to get close to a moving target by adaptively tracking the target location. Some numerical simulation results show that the proposed low-cost system works well in a multi-path environment.
Geoscience and Remote Sensing Symposium (IGARSS), 2010 IEEE International; 08/2010
